Glass grinding apparatus



1936- J. H. GRIFFIN 2,041,642

GLASS GRINDING APPARATUS Filed Jan. 20, 1936 Afro/m5 M 777m' KM 4. 1.4:

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Patented May 19, 1936 TED STATES GLASS GRINDING APPARATUS James Harris Griflin, St. Helens, England, assignor to Pilkington Brothers Limited, Liverpool, England, a company of Great Britain Application January 20, 1936, Serial No. 59,968 In Great Britain January 21, 1935 2 Claims.

This invention relates to glass grinding apparatus and has for its object an improved apparatus for supplying abrasive to rotary grinding tools operating on the under surface of glass.

It has been proposed to supply abrasive, commonly sand and water, through a central hole in the shaft of the grinding tool to the central space in the operative face of the tool, whence it flows through grooves in the face. It has been found that, when abrasive is supplied in this way, the grinding action of the tool is irregular unless the pressure at which the abrasive is supplied is closely controlled. To take an example, with a grinding tool 2 metres in diameter, with a pressure of the abrasive of 10 cm. of water above the face of the tool, the total pressure tending to lift the glass from the face of the tool would be over 300 kg. if the pressure were operative over the whole area of the tool, and is, in any case, a large pressure. Since grinding tools operating on the under surface of glass are used in general in conjunction with similar tools operating on the upper surface, any substantial pressure due to the abrasive supply between the glass and the operative face of the lower grinding tool causes differences in the grinding action of the upper and lower grinding tools.

According to the invention, the abrasive is fed to the grinding tool from a container having a contant level device adapted to maintain the level substantially that of the operative face of the tool. Preferably the container is so connected with the grinding tool that it partakes of its vertical movements.

The accompanying drawing is a vertical cross section of a grinding tool operating on the under surface of a strip of glass, showing the device for feeding abrasive. The strip of glass l is operated on by the blocks 2 of the lower grinding tool and the blocks 3 of the upper grinding tool. The blocks 2 are attached to the disc 4 of the tool, the shaft 5 of which runs in bearings 6 in a tubular casing 1. This casing is adapted to slide in a tubular frame 9 which is supported on girders 8. The shaft 5 is rotated by a bevel wheel I engaging a pinion ll carried. in a cage l2 on the end of the tubular casing l. The height of the tool is adjusted by means of the bevel wheel l3, which contains a nut engaging the screw-threaded rod 14, which abuts at l against the cage l2.

The shaft 5 is hollow and its bore communicates above with the central space IS in the tool, from which grooves 11 run between the blocks 2. The bore communicates below with the stuffing box Ill.

The apparatus described above is known from Patent No. 1,729,498.

From the stuffing box I8 a pipe I 9 communicates with a container supported on the casing I of the shaft 5 by the bracket 22. The container 20 receives abrasive from the pipe 23, which communicates with the usual sand-grading tanks. The container 29 is provided with an overflow opening 24 approximately at the level of the operative face of the grinding tool, adapted to prevent the level of abrasive in the container from rising above this level. By regulating the supply of abrasive through the pipe 23, so as to maintain a small overflow through the opening 24, the level of the abrasive in the container 20 may be kept approximately at the level of the face of the grinding tool. Alternatively the container may be provided with a float operating a valve in the supply pipe 23.

It is not essential that the container 20 should be attached to the grinding tool, since any vertical movement of the tool is very small, and, by making the pipe 19 flexible, it may be fixed relatively to the girders 8.

When the sides of the blocks 2 are so shaped as to exert an upward force on the abrasive in contact with them, the level of the abrasive in the container 20 may be maintained slightly below the face of the grinding tool. When the blocks do not exert upward force on the abrasive, the level must be maintained at or slightly above the face of the grinding tool.

In the event that the flow of abrasive from the container to the central space I6 is restricted to an extent that an appreciable head is absorbed by the flow, then the level in the container must be above the level of the face of the tool by the amount of the head so lost.

Having described my invention, I declare that what I claim and desire to secure by Letters Patent is:-

1. Glass grinding device comprising a grinding tool operating on the upper surface of the glass, a grinding tool operating on the lower surface of the glass, means for rotating the said lower tool and means for adjusting its height, an abrasive mixture container with constant level device, adapted to maintain the level of the abrasive mixture approximately at the level of the operative surface of the lower tool and a communication between the said container and a central space in the lower tool.

2. Glass grinding device as in claim 1, comprising a support for the abrasive mixture container attached to a part of the lower tool which moves when the height is adjusted but does not rotate.

JAMES HARRIS GRIFFIN. 

